Previous studies have shown that modulation of the receptor-mediated cannabinoid system during neuroinflammation can produce potent neuroprotective and anti-inflammatory effects. However in this context, little is known about how selective activation of the cannabinoid type-2 receptor (CB2R) affects the activated state of the brain endothelium and blood brain barrier (BBB) function. Using human brain tissues and primary human brain endothelial cells (BMVEC) we demonstrate that the CB2R is highly upregulated during inflammatory insult. We then examined whether the CB2R agonists could attenuate inflammatory responses at the BBB using a mouse model of LPS-induced encephalitis and highly selective CB2R agonists. Visualization by intravital microscopy revealed that administration of JWH133 or a novel resorcinol-based compound O-1966, greatly attenuated leukocyte adhesion in surface pial vessels and in deep ascending cortical post-capillary venules. BBB permeability assessments with small and large fluorescent tracers showed that CB2R agonists were effective at preventing barrier leakiness after LPS administration. To determine whether the effects by CB2R agonists on barrier protection are not only due to the CB2R modulation of immune cell function, we tested the agonists in-vitro with barrier forming primary BMVEC. Remarkably, the addition of CB2R agonist increased trans-endothelial electrical resistance and increased the amount of tight junction protein present in membrane fractions. Furthermore, CB2R agonists decreased the induction of ICAM-1 and VCAM-1 surface expression in BMVEC exposed to various pro-inflammatory mediators. Together, these results suggest that pharmacological CB2R ligands offer a new strategy for BBB protection during neuroinflammation.

Methamphetamine (METH), a potent stimulant with strong euphoric properties, has a high abuse liability and long-lasting neurotoxic effects. Recent studies in animal models have indicated that METH can induce impairment of the blood brain barrier (BBB), thus suggesting that some of the neurotoxic effects resulting from METH abuse could be the outcome of barrier disruption. Here we provide evidence that METH alters BBB function via direct effects on endothelial cells and explore possible underlying mechanisms leading to endothelial injury. We report that METH increases BBB permeability in vivo, and exposure of primary human microvascular endothelial cells (BMVEC) to METH diminishes tightness of BMVEC monolayers in a dose- and time-dependent manner by decreasing expression of cell membrane associated tight junction (TJ) proteins. These changes were accompanied by enhanced production of reactive oxygen species, increased monocyte migration across METH-treated endothelial monolayers, and activation of myosin light chain kinase (MLCK) in BMVEC. Anti-oxidant treatment attenuated or completely reversed all tested aspects of METH induced BBB dysfunction. Our data suggest that BBB injury is caused by METH-mediated oxidative stress, which activates MLCK and negatively affects the TJ complex. These observations provide a basis for antioxidant protection against brain endothelial injury caused by METH exposure.

Recent studies have revealed a positive correlation between astrocyte apoptosis and rapid disease progression in persons with neurodegenerative diseases. Glycogen synthase kinase 3␤ (GSK-3␤) is a molecular regulator of cell fate in the central nervous system and a target of the phosphatidylinositol 3-kinase (PI-3K) pathway. We have therefore examined the role of the PI-3K pathway, and of GSK-3␤, in regulating astrocyte survival. Our studies indicate that inhibition of PI-3K leads to apoptosis in primary cortical astrocytes. Furthermore, overexpression of a constitutively active GSK-3␤ mutant (S9A) is sufficient to cause astrocyte apoptosis, whereas an enzymatically inactive GSK-3␤ mutant (K85M) has no effect. In light of reports on the interplay between GSK-3␤ and nuclear factor B (NF-B), and because of the antiapoptotic activity of NF-B, we examined the effect of GSK-3␤ overexpression on NF-B activation. These experiments revealed strong inhibition of NF-B activation in astrocytes upon overexpression of the S9A, but not the K85M, mutant of GSK-3␤. This was accompanied by stabilization of the NF-B-inhibitory protein, IB␣ and down-regulation of IB kinase (IKK) activity. These findings therefore implicate GSK-3␤ as a regulator of NF-B activation in astrocytes and suggest that the pro-apoptotic effects of GSK-3␤ may be mediated at least in part through the inhibition of NF-B pathway.

Methamphetamine (METH) abuse is known to be associated with an inordinate rate of infections. Although many studies have described the association of METH exposure and immunosuppression, so far the underlying mechanism still remains elusive. In this study, we present evidence that METH exposure resulted in mitochondrial oxidative damage and caused dysfunction of primary human T cells. METH treatment of T lymphocytes led to a rise in intracellular calcium levels that enhanced the generation of reactive oxygen species. TCR-CD28 linked calcium mobilization and subsequent uptake by mitochondria in METH-treated T cells correlated with an increase in mitochondrion-derived superoxide. Exposure to METH-induced mitochondrial dysfunction in the form of marked decrease in mitochondrial membrane potential, increased mitochondrial mass, enhanced protein nitrosylation and diminished protein levels of complexes I, III, and IV of the electron transport chain. These changes paralleled reduced IL-2 secretion and T cell proliferative responses after TCR-CD28 stimulation indicating impaired T cell function. Furthermore, antioxidants attenuated METH-induced mitochondrial damage by preserving the protein levels of mitochondrial complexes I, III, and IV. Altogether, our data indicate that METH can cause T cell dysfunction via induction of oxidative stress and mitochondrial injury as underlying mechanism of immune impairment secondary to METH abuse.